Among 41 male-dominated occupations, firefighters have the third highest prevalence rate of obesity. Few studies have examined the roles of working conditions and health behaviors of firefighters in obesity. In addition, few validated instruments -- a methodological prerequisite for obesity studies in firefighters -- are available that specifically assess the unique working conditions and health behaviors of firefighters who work on a 24 hour-shift system. Our long-term goals are to elucidate the roles of working conditions and health behaviors in the development of obesity among firefighters and to use this information to design and conduct intervention studies that lower CVD risk factors among firefighters by changing working conditions and health behaviors. The main aims of this proposal are a) to develop and validate a firefighter-relevant work and health questionnaire using qualitative and quantitative methods in firefighters enrolled in the Orange County Fire Authority (OCFA) Wellness Fitness (WEFIT) Program, b) to use this questionnaire in an epidemiological study to explore whether adverse working conditions and health behaviors are risk factors for obesity in firefighters, and c) to explore the interrelations between working conditions and health behaviors as they relate to obesity. A supplementary objective is to evaluate the strengths and weaknesses of Body Mass Index (BMI) as a measurement (commonly used as a surveillance measure of obesity in many WEFIT programs for firefighters) in comparison with skinfold-based body fat percent. For the purposes of this study, we will use a participatory action research (PAR) approach to build a work group of firefighters and researchers to develop and validate a questionnaire for assessing working conditions and health behaviors of firefighters. The developed questionnaire will be completed by about 350 OCFA firefighters over 15 months. A subsample of the firefighters (n=80) will be recruited to complete a 3-day food record and to wear an accelerometer during the same 3 days, and to fill in a short-form of the questionnaire for a one-week test and retest reliability. In addition, for analyses, the records of the WEFIT medical and fitness exams (Body Mass Indexes, body fat %, VO2 max, blood pressures, and blood lipid profiles) of the participants and archival records of 2004-2011 annual calls by each local OCFA fire station will be linked to the exposure profiles. At the end of this project a firefighter-relevant work and health questionnaire will have been developed, along with several recommendations to reduce the obesity risk of OCFA firefighters. We propose this as an exploratory study which meets the public safety sub-sector strategic goals 1.4 and 1.5 of the National Occupational Research Agenda (NORA) and the Research to Practice (r2P) initiatives at the National Institute for Occupational Safety and Health. 1 PUBLIC HEALTH RELEVANCE: Developing a firefighter work and health questionnaire utilizing PAR will significantly facilitate studies on the relationships between work, health behaviors, and CVD risk in firefighters. Identify occupational and behavioral risk factors for obesity in firefighters is an essential first step for establishing effective intervention programs for obesity in firefighters. The comparative methodological investigation on obesity measures in firefighters will be helpful in developing reliable and valid medical surveillance guidelines about obesity in almost 1.1 million professional and voluntary firefighters in the US.